We’ve recently had a couple of situations arise with SBC rear cam bearings where the cam bearing kit we received contained the wrong rear cam bearing for our application. One engine was a ’57 Chevy 283 and most recently it occurred with a ’63 Corvette 327. Fortunately we discovered the problem before installing the bearings. We wanted to pass this information on to our readers to hopefully save them some grief and money should they encounter the same thing.
This affects the following small block Chevy engines:
These ’55-’63 SBCs had an oil groove in the rear cam journal bore that was offset towards the back of the block (see picture).
When the engine was new, the rear cam bearing had a corresponding hole in the bearing that was also offset to the back of the block. If you installed the bearing backwards, the rear cam journal galley would be covered and no oil would lubricate the journal. Eventually Chevy made a running change to drill two holes in the bearing (front and rear) so oil would get through whichever way you installed it (see picture).
Starting in ’64 though, Chevy centered the groove in the rear cam journal bore. Therefore if you try using a cam bearing set designed for ’64 and later engines on a ’63 or earlier block, very little or no oil will make its way to the rear cam journal and damage will result.
So if you are installing new cam bearings in a ’55-’63 SBC, order the Clevite SH-287S bearing set (or comparable set) and you won’t have any rear cam bearing oiling issues.